Soldiers of the U.S. Army 23rd chemical battalion salute during a ceremony April 4, 2013, in South Korea. / Lee Jin-man, AP

by Tom Vanden Brook, USA TODAY

by Tom Vanden Brook, USA TODAY

WASHINGTON - The Army would be slashed by more than 100,000 soldiers to a force of 420,000 by 2019 under budget plans set to be unveiled next month. It is a level far below what Army leaders have said they would need to ensure they can fight one major war.

The Army currently has 528,000 soldiers and had been scheduled to drop to 490,000 troops by 2019. The 420,000 level reflects Pentagon planning based on automatic budget cuts that will reduce military spending by about $500 billion over the decade unless Congress restores the funding.

This fall, Army chief of staff Gen. Raymond Odierno warned top Pentagon officials in a briefing that a force of 450,000 soldiers would be "too small" and at "high risk to meet one major war," according to documents obtained by USA TODAY. The Army could not adequately protect the country and fight abroad at 420,000 soldiers, the documents stated.

Since then, the chiefs of the services have been told to list the missions they won't be able to accomplish with diminished budgets, a senior Pentagon official said on condition of anonymity because the budget will not be released for weeks.

For the Army, a force of 420,000 means that it could respond to a conflict, such as one on the Korean peninsula, but won't be able to keep up the fight for long without a significant call up of reserve forces, said another senior military officer who also spoke on condition of anonymity to discuss the plans.

The other services will be reduced in size as well. The Navy will be able to continue to shift its focus to the Pacific but with far fewer ships, and its presence in the Persian Gulf will be lessened.

Even at the reduced numbers, the U.S. military is more than a match for any potential foe, said Gordon Adams, a professor at American University and a budget official in the Clinton Administration.

"Who else that we are going to fight in a ground war has 420,000 soldiers?" Adams said in an e-mail. "Silly, really. Of course, we can."

If long-term budget cuts are rolled back, the services won't have to cut so deeply into their troop levels. The Pentagon forecasts significant shortfall in its budgets for the next several years. In the current fiscal year, it sought $526 billion for costs that did not include the war in Afghanistan. The budget cuts known as "sequestration" would have lowered that to $475 billion. A budget deal in Congress restored some funds, giving the Pentagon $496 billion.

The shrinking budget has resulted in jockeying by the services to secure the most funding. Last month, for example, a National Guard leader said the Army could be cut to 420,000 soldiers if the Guard was allowed to expand.

The Army grew to a force of about 570,000 soldiers at the height of fighting in Afghanistan and Iraq. It was strained greatly in 2007 when President Bush ordered the surge of troops in Iraq. Deployments that had been one year long were extended for some soldiers to 15 months.

The White House strategy assumes that the U.S. military will no longer be engaged in long-term operations that are troop intensive. Instead, it envisions smaller, nimbler forces that deploy for short periods.